This research study has been designed to evaluate the safety and effectiveness of T-20 in the treatment of HIV infection. This study allows people who received T-20 in a previous study to take T-20 for up to 48 weeks. During the past several years, 13 antiretroviral medicines have been approved by the FDA for the treatment of HIV-1 infected individuals. These drugs approved so far belong to one of two groups: either reverse transcriptase inhibitors or protease inhibitors. Researchers know that people who take these drugs, either alone or in various combinations, often develop resistance to the drugs over time. Furthermore, some of the currently approved drugs have side effects that are potentially harmful. Therefore, there is a need for the development of new, safe drugs that are different from those already in use. T-20 is a special type of protein (peptide) that is being developed as a new approach for the treatment of HIV infection. T-20 has been shown to block HIV-1 replication in test tubes and has been tested in subjects with HIV-1 infection. T-20 works by keeping the virus from binding to the surface of certain cells in the immune system.